1. Field of the Invention
The present invention pertains primarily to fastening means for use on bolts, screws, nuts and the like, and more particularly to fastening means which include an adhesive composition.
2. Description of the Prior Art
The state of the art is believed to be indicated by the following cited references: U.S. Pat. No. 3,179,143--Schultz et al; U.S. Pat. No. 3,642,937--Deckert et al; U.S. Pat. No. 3,746,068--Deckert et al; U.S. Pat. No. 3,485,132--Hanny et al; U.S. Pat. No. 3,639,137--Marinelli; U.S. Pat. No. 2,939,805--Johnson; U.S. Pat. No. 3,061,455--Anthony; U.S. Pat. No. 3,251,708--Schmetterer et al; U.S. Pat. No. 3,467,544--Marinelli et al; U.S. Pat. No. 3,043,820--Krieble; U.S. Pat. No. 3,046,262--Krieble; U.S. Pat. No. 3,704,264--Gorman; U.S. Pat. No. 3,293,977--Dalton et al; U.S. Pat. No. 3,489,599--Krieble; U.S. Pat. No. 2,895,950--Krieble; U.S. Pat. No. 3,425,988--Gorman; U.S. Pat. No. 3,275,579--Stierli et al; U.S. Pat. No. 3,018,258--Meier et al; and U.S. Pat. No. 3,218,305--Krieble.
Generally, adhesive compositions for use in fastener retention have consisted of several different adhesive families depending upon the application and the assembly requirements. Typical of the prior art are the adhesives such as heat curing epoxies, anaerobic adhesives, deformable plastic strips placed over the fasteners, or two separate strips of adhesive coated onto the fastener which are then mixed upon installation of the fastener. Some prior art systems have encapsulated one component of a two-component epoxy system with the mixing of such a system being accomplished when the fastener was installed.
One major consideration in choosing a fastener retention system is the ease with which it can be integrated to the assembly process. If the adhesive is not pre-applied to the fastener, it must be applied just prior to assembly and often is wet, tacky and rather messy. If the adhesive can be pre-applied, it could be dried to provide for handling and transportation prior to assembly. Some prior art adhesive systems are dried by baking, which is normally an expensive step in the process and uses valuable energy. Other prior art systems use an air dry, but most take a considerable amount of time, and require storage during the drying period.
Other requirements of various industries such as the automotive industry require that the fasteners be corrosion resistant. As an example, some automotive manufacturers' specifications for bolts require that the bolts be coated with phosphate and oil to help them resist corrosion. Many of the prior art adhesives appear to destroy the phosphate and oil coating thus reducing the corrosion resistance of the bolt.
An additional problem encountered in many of the applications of such adhesive compositions in fastener retention is that of multiple usage. Multiple usage is the term used to describe repeated installation and removal of the same fastener. Typical of the industry tests of such properties is the "fifth off" test. This test measures the capability of the same adhesive coated fastener to be used five times. The fifth off value is the break away torque encountered in an effort to loosen the bolt after the fifth installation. Most prior art systems can only be used once, or at best, twice.
Another disadvantage of many prior art systems is that of the high torque requirements for installation. Normally, coating a fastener or the like with an adhesive or a deformable plastic strip causes the torque required to install the fastener to increase substantially. Very often this puts undue constraints on the assembly process and may even cause stripping or shearing of fasteners during installation.
It is a principle object of the present invention therefore to provide an improved adhesive composition for use as a fastening means on bolts, nuts, screws and the like.
Another object is to provide a new and improved fastener product which includes a unique adhesive system.
It is a further object of the present invention to provide a relatively inexpensive, non-tacky adhesive composition which is applied as a single composition in a high speed assembly process.
It is another object of the present invention to provide an adhesive composition which does not destroy corrosion resistant coatings such as phosphate and oil and also has good multiple usage properties.
Other objects, features and advantages of the present invention will become apparent from the subsequent description, and examples, and the appended claims taken in conjunction with the accompanying drawings.